The fibre channel ("FC") is an architecture and protocol for a data communication network for interconnecting a number of different combinations of computers and peripheral devices. The FC supports a variety of upper-level protocols, including the small computer systems interface ("SCSI") protocol. A computer or peripheral device is linked to the network through an FC port and copper wires or optical fibres. An FC port includes a transceiver and an interface controller, and the computer peripheral device in which the FC port is contained is called a "host." The FC port exchanges data with the host via a local data bus, such as a peripheral computer interface ("PCI") bus. The interface controller conducts lower-level protocol exchanges between the fibre channel and the computer or peripheral device in which the FC port resides.
Because of the high bandwidth and flexible connectivity provided by the FC, the FC is becoming a common medium for interconnecting peripheral devices within multi-peripheral-device enclosures, such as redundant arrays of inexpensive disks ("RAIDs"), and for connecting multi-peripheral-device enclosures with one or more host computers. These multi-peripheral-device enclosures economically provide greatly increased storage capacities and built-in redundancy that facilitates mirroring and fail over strategies needed in high-availability systems. Although the FC is well-suited for this application with regard to capacity and connectivity, the FC is a serial communications medium. Malfunctioning peripheral devices and enclosures can, in certain cases, degrade or disable communications. A need has therefore been recognized for methods to improve the ability of FC-based multi-peripheral-device enclosures to isolate and recover from malfunctioning peripheral devices, and for improving the ability of systems including one or more host computers and multiple, interconnected FC-based multi-peripheral-device enclosures to isolate and recover from a malfunctioning multi-peripheral-device enclosure. A need has also been recognized for additional communications and component redundancies within multi-peripheral-device enclosures to facilitate higher levels of fault-tolerance and high-availability.